Even if you’re a company fan, resist the urge to use a trademark in your domain name.
Compete.com shows that GM-Volt.com gets about 75,000 visits a month, which is nothing to sneeze at. It probably brings in a bit of revenue for the site owner, too, which is why I would never recommend starting a site that uses a brand name like this. GM can quite possibly get the domain name, either through a cheap and fast UDRP or through a lawsuit.
But wait — isn’t this site good for building GM’s brand? Perhaps, but it’s littered with ads for GM’s competitors. Right now I see ads for Ford and Lexus. Even a disclaimer message saying the site isn’t affiliated with General Motors Company is turned into a contextual ad for Ford:
Some companies have made a business out of similar car enthusiast sites, including publicly traded Internet Brands. But even they acknowledge there’s some risk in what they do.
My advice: go ahead and create a fan site. But don’t include trademarks in your domain name.